65

Application Information

Circuit Description

The block diagram of the CA3193 amplifier shows the

voltage gain and supply current for each of its fouramplifier

stages. Simplified and complete schematic diagrams of the

CA3193 amplifier are shown in Figures 5 and 6, respectively.

A quad of physically cross-connected NPN transistors

5 and 6); this arrangement contributes to the low input offset-

voltage characteristics of the amplifier. The ultra-high gain

provided in the first stage ensures that subsequent stages

cannot significantly influence the overall offset-voltage

characteristics of the amplifier. High load impedances for the

thereby contributing to the high gain developed in the stage.

The second stage of the amplifier consists of a differential

M0S/FETs, their loading on the first stage is quite low,

thereby making an additional contribution to the high gain

developed in the first stage. The second stage is also config-

ured to convert its differential signal to a single-ended output

to drive subsequent gain stage.

The third stage of the amplifier consists of Darlington-

driving the quasi-complementary Class AB output stage

circuit protection is activated by voltage drops developed

acrossthe 60

and shunts the base drive from the bases of the output stage

Internal frequency compensation for the CA3193 amplifier is

provided by two internal networks, a 6pF capacitor

connected between the input-stage transistor collectors and

the node between the third and output stagesand a second

network, consisting of a 20pF capacitor in series with a

7.5k

Ω resistor connected between the input and output

nodes of the third stage.

Offset Voltage Nulling

The input offset voltage can be nulled to zero by any of the

three methodsshown in the table below. A 10K potentiome-

ter betweenterminals1and5, withits wiper returned toV-,

will provide a gross nulling for all types. For finer nulling,

either of the other two circuits shown below may be used,

thus providing simpler improved resolution for all types.

CAUTION: The CA3193 amplifiers will be damaged if they are

plugged into op amp circuits employing nulling with respect to the

V+ supply bus.

Offset Voltage Nulling

OFFSET NULLING

CIRCUITS

TYPE

RESISTOR R VALUE

RESISTOR R VALUE

RESISTOR R VALUE

CA3193A

10K

50K

10K

CA3193

10K

20K

5K

Gross Offset Adjustment

Finer Offset Adjustments

1

5

R

V-

1

5

10K

V-

R

1K

V-

R

R

1

5

CA3193, CA3193A